Many 1940s-60s houses will have been altered – for example to provide indoor-outdoor flow – but few have been brought up to modern energy efficiency standards.
State houses that have been sold into private ownership may have had significant alterations carried out, especially in areas where growing property values have justified it. The biggest indication of their origins may be from the surrounding houses, as state housing tended to be built in clusters or developments.
Privately built housing from the 1940s-60s is also likely to have undergone some alteration.
However, despite the fact that both state and private houses generally had no insulation installed, and that private housing was generally built without consideration for orientation to benefit from solar gain, any alterations are likely to have focused more on increasing living space and meeting modern lifestyle requirements than on energy efficiency.
Although houses classified as ‘the New Zealand style’ were innovative and are more likely than mass produced houses to have retained their principal features, they are also likely to fall short of current energy efficiency requirements as insulation was either not included or minimal by today’s standards. In addition, the use of larger areas of single glazing means that the there will be significant heat loss through the glass.
Where renovations to improve energy efficiency have been carried out, depending on when they occurred they are likely to be the installation of roof space insulation where access is available, and possibly underfloor insulation. The cost of installing wall insulation is generally not justified. While existing glazing may have been replaced by double-glazed units, the large areas of glazing means this is not common.
It is likely that a large proportion of the houses built during the 1940s-1960s will require upgrading to bring them up to current standards of energy efficiency.
An advantage when renovating houses built during this period is that the original drawings are often available – something that was typically lacking for houses built in earlier periods.